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The many-worlds theory, explained + Universe is not purely mathematical in nature

#1
C C Offline
No, The Universe Is Not Purely Mathematical In Nature
https://www.forbes.com/sites/startswitha...7e23211653



The Many-Worlds Theory, Explained
https://thereader.mitpress.mit.edu/the-m...ds-theory/

EXCERPTS (John Gribbin): . . . If you have heard of the Many Worlds Interpretation (MWI), the chances are you think that it was invented by the American Hugh Everett in the mid-1950s. In a way that’s true. He did come up with the idea all by himself. But he was unaware that essentially the same idea had occurred to Erwin Schrödinger half a decade earlier. Everett’s version is more mathematical, Schrödinger’s more philosophical, but the essential point is that both of them were motivated by a wish to get rid of the idea of the “collapse of the wave function,” and both of them succeeded.

As Schrödinger used to point out to anyone who would listen, there is nothing in the equations (including his famous wave equation) about collapse. That was something that Bohr bolted on to the theory to “explain” why we only see one outcome of an experiment — a dead cat or a live cat — not a mixture, a superposition of states. [See Origin of Copenhagen Interpretation.] But because we only detect one outcome — one solution to the wave function — that need not mean that the alternative solutions do not exist. In a paper he published in 1952, Schrödinger pointed out the ridiculousness of expecting a quantum superposition to collapse just because we look at it. It was, he wrote, “patently absurd” that the wave function should “be controlled in two entirely different ways, at times by the wave equation, but occasionally by direct interference of the observer, not controlled by the wave equation.”

[...] There is no collapse of the wave function. Schrödinger anticipated the reaction of his colleagues in a talk he gave in Dublin, where he was then based, in 1952. ... In fact, nobody responded to Schrödinger’s idea. It was ignored and forgotten, regarded as impossible.

So Everett developed his own version of the MWI entirely independently, only for it to be almost as completely ignored. But it was Everett who introduced the idea of the Universe “splitting” into different versions of itself when faced with quantum choices, muddying the waters for decades. [...] Everett did point out that since no observer would ever be aware of the existence of the other worlds, to claim that they cannot be there because we cannot see them is no more valid than claiming that the Earth cannot be orbiting around the Sun because we cannot feel the movement.

Everett himself never promoted the idea of the MWI. [...] It wasn’t until the late 1960s that the idea gained some momentum when it was taken up and enthusiastically promoted by Bryce DeWitt, of the University of North Carolina ... The power of the interpretation began to be appreciated even by people reluctant to endorse it fully.

[...] The precise version of the MWI came from David Deutsch, in Oxford, and in effect put Schrödinger’s version of the idea on a secure footing, although when he formulated his interpretation, Deutsch was unaware of Schrödinger’s version. ... Deutsch became a pioneer in the field of quantum computing, not through any interest in computers as such, but because of his belief that the existence of a working quantum computer would prove the reality of the MWI.

This is where we get back to a version of Schrödinger’s idea. In the Everett version of the cat puzzle, there is a single cat up to the point where the device is triggered. Then the entire Universe splits in two. [...] Deutsch argues that when two or more previously identical universes are forced by quantum processes to become distinct ... there is a temporary interference between the universes, which becomes suppressed as they evolve. It is this interaction that causes the observed results of ... experiments.

[...] What makes a quantum computer qualitatively different from a conventional computer is that the “switches” inside it exist in a superposition of states [...] either on or off, corresponding to the digits 1 or 0. ... Each switch in a quantum computer, however, is an entity that can be in a superposition of states. ... they are both ... 0 and 1 [...at the same time...] Each switch is called a qbit, pronounced “cubit.”

[...] A computer with just 300 qbits would be equivalent to a conventional computer with more bits than there are atoms in the observable Universe. How could such a computer carry out calculations? The question is more pressing since simple quantum computers, incorporating a few qbits, have already been constructed and shown to work as expected. They really are more powerful than conventional computers with the same number of bits.

Deutsch’s answer is that the calculation is carried out simultaneously on identical computers in each of the parallel universes corresponding to the superpositions.[...] when we build a 300-qbit machine ... we will, if Deutsch is right, be involving a “collaboration” between more universes than there are atoms in our visible Universe. It is a matter of choice whether you think that is too great a load of metaphysical baggage. But if you do, you will need some other way to explain why quantum computers work.

Most quantum computer scientists prefer not to think about these implications. But there is one group of scientists who are used to thinking of even more than six impossible things before breakfast — the cosmologists. Some of them have espoused the Many Worlds Interpretation as the best way to explain the existence of the Universe itself.

Their jumping-off point is the fact, noted by Schrödinger, that there is nothing in the equations referring to a collapse of the wave function. And they do mean the wave function; just one, which describes the entire world as a superposition of states — a Multiverse made up of a superposition of universes. [...] Cosmologists are excited by this, not because they are included in the wave function, but because this idea of a single, uncollapsed wave function is the only way in which the entire Universe can be described in quantum mechanical terms while still being compatible with the general theory of relativity.

The universal wave function describes the position of every particle in the Universe at a particular moment in time. But it also describes every possible location of those particles at that instant. And it also describes every possible location of every particle at any other instant of time, although the number of possibilities is restricted by the quantum graininess of space and time. Out of this myriad of possible universes, there will be many versions in which stable stars and planets, and people to live on those planets, cannot exist. But there will be at least some universes resembling our own, more or less accurately, in the way often portrayed in science fiction stories. Or, indeed, in other fiction. Deutsch has pointed out that according to the MWI, any world described in a work of fiction, provided it obeys the laws of physics, really does exist somewhere in the Multiverse. There really is, for example, a “Wuthering Heights” world (but not a “Harry Potter” world).

That isn’t the end of it. The single wave function describes all possible universes at all possible times. But it doesn’t say anything about changing from one state to another. Time does not flow. Sticking close to home, Everett’s parameter, called a state vector, includes a description of a world in which we exist, and all the records of that world’s history, from our memories, to fossils, to light reaching us from distant galaxies, exist. There will also be another universe exactly the same except that the “time step” has been advanced by, say, one second (or one hour, or one year). But there is no suggestion that any universe moves along from one time step to another. There will be a “me” in this second universe, described by the universal wave function, who has all the memories I have at the first instant, plus those corresponding to a further second (or hour, or year, or whatever). But it is impossible to say that these versions of “me” are the same person. Different time states can be ordered in terms of the events they describe, defining the difference between past and future, but they do not change from one state to another. All the states just exist. Time, in the way we are used to thinking of it, does not “flow” in Everett’s MWI... (MORE - details)

RELATED: Six Impossible Things: The Mystery of the Quantum World, by John Gribbin
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#2
Catastrophe Offline
"Schrödinger pointed out the ridiculousness of expecting a quantum superposition to collapse just because we look at it."

The most sensible statement I have heard (IMHO) about Quantum Mechanics!

Why not just say the truth. The cat is in an indeterminate state. It is neither alive nor dead.
Its state of life mathematically is approximately 50% depending on the details of the experiment. (The actual mechanism might be biased).
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#3
confused2 Offline
(May 22, 2020 05:03 AM)Catastrophe Wrote: "Schrödinger pointed out the ridiculousness of expecting a quantum superposition to collapse just because we look at it."

The most sensible statement I have heard (IMHO) about Quantum Mechanics!

Why not just say the truth. The cat is in an indeterminate state. It is neither alive nor dead.
Its state of life mathematically is approximately 50% depending on the details of the experiment. (The actual mechanism might be biased).
If only it was so simple. The Double slit experiment is a classic conundrum where knowing the path of the photon (which slit it went through) destroys the interference pattern. The delayed choice setup allows the path (optionally) to be determined after (8ns later) the interference pattern has been detected (or diffraction pattern if no interference).
If the path is detected (later) then the (earlier) interference pattern is not seen.

https://en.wikipedia.org/wiki/Delayed-ch...tum_eraser

The double slit experiment is one of my favourites. Maybe new thread if you would like to discuss it further.
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#4
confused2 Offline
Cat Wrote:Schrödinger pointed out the ridiculousness of expecting a quantum superposition to collapse just because we look at it.
OK a swipe at 'detection'. This is my interpretation of an interpretation - not complete but it might be interesting.

A 'detection' (for now) involves a process that isn't reversible. For example If a detector makes a click when a photon is detected you can't make a photon by making a click in the vicinity of the detector. If a photon hits the back of the eye and causes a chemical change the energy of the photon goes into making the chemical change and the photon is destroyed in the process. The chemical change isn't reversible. If a photon bounces off the nice shiny lens at the front of the eye you don't see it and the photon stays in play.

Dwelling on the standard Double Slit Experiment - the probability of detecting a photon at any of an infinite number of points can be calculated with great precision. What is surprising is that removing the photon from play by an irreversible process means it won't be detected anywhere else - the probability 'field' vanishes (or collapses) instantly. I don't think Einstein was very pleased with photons because 'instantly' and special relativity don't work well together.
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#5
Secular Sanity Offline
(May 29, 2020 05:36 PM)confused2 Wrote:
Cat Wrote:Schrödinger pointed out the ridiculousness of expecting a quantum superposition to collapse just because we look at it.
OK a swipe at 'detection'.  This is my interpretation of an interpretation - not complete but it might be interesting.

A 'detection' (for now) involves a process that isn't reversible. For example If a detector makes a click when a photon is detected you can't make a photon by making a click in the vicinity of the detector. If a photon hits the back of the eye and causes a chemical change the energy of the photon goes into making the chemical change and the photon is destroyed in the process. The chemical change isn't reversible. If a photon bounces off the nice shiny lens at the front of the eye you don't see it and the photon stays in play. 

Dwelling on the standard Double Slit Experiment - the probability of detecting a photon at any of an infinite number of points can be calculated with great precision. What is surprising is that removing the photon from play by an irreversible process means it won't be detected anywhere else - the probability 'field' vanishes (or collapses) instantly. I don't think Einstein was very pleased with photons because 'instantly' and special relativity don't work well together.

Even if the photons are sent through the slits one at a time, there’s still a wave pattern. One photon from this pair should go on to create the interference pattern, while the other one travels to the detector.


https://www.youtube-nocookie.com/embed/p-MNSLsjjdo
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#6
confused2 Offline
SS Wrote:Even if the photons are sent through the slits one at a time,
That's just one photon arriving.
SS Wrote:One photon from this pair should go on to create the interference pattern,
There's only one photon now with two paths.The two paths are what creates the interference pattern.
SS Wrote:.. while the other one travels to the detector.
There's still only one photon - if detected it's game over.
What happens to the rest of the wave/interference pattern when the photon is detected?
Nobody knows.
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#7
Secular Sanity Offline
(May 30, 2020 11:16 AM)confused2 Wrote:
SS Wrote:Even if the photons are sent through the slits one at a time,
That's just one photon arriving.
SS Wrote:One photon from this pair should go on to create the interference pattern,
There's only one photon now with two paths.The two paths are what creates the interference pattern.
SS Wrote:.. while the other one travels to the detector.
There's still only one photon - if detected it's game over.
What happens to the rest of the wave/interference pattern when the photon is detected?
Nobody knows.

No, C2, that's not what I'm saying. You still end up with an interference pattern when only one photon is sent through at a time. So, theoretically, the single photons hitting the screen during observation (wave function collapse) should still be able to produce a single-particle interference pattern or so they say.

Are you suggesting that the photons are entangled and that we’re disrupting the phase of the interference pattern? That could be, if they’re correlated with the polarization state of the trigger photon.

Did you know that interference and diffraction are basically the same thing? It’s only a matter of degree. Feynman said that when there are only a few sources, say two, we call it interference (as in Young’s slits), but with a large number of sources, the process can be labelled diffraction.

You might think I’m nuts because Penrose is a little wackadoodle in areas like consciousness, but I am fond of his interpretation. Light has energy, which is equivalent to mass. So, it should be able to produce a gravitational field, right?

Did you know that gravitational waves are also affected by gravity? We all know that curvature is what determines how everything moves through the Universe. Gravitational waves behave just like electromagnetic waves. They have energy, a wavelength, they’re massless and travel at the same speed. They get stretched out due to the expansion just like electromagnetic waves. They even experience time dilation. Weird, eh?

Wouldn’t it be wild if what we were actually observing was the interaction between a graviton and photon or an electromagnetic wave and gravitational wave? It would resemble the superposition principle, wouldn't it? What if the wavefunction that entangles particles was in fact, its gravitational wave.

Just a thought.

Quote:In Einstein's theory, any object that has mass causes a warp in the structure of space and time around it. This warping produces the effect we experience as gravity. Penrose points out that tiny objects, such as dust specks, atoms and electrons, produce space-time warps as well. Ignoring these warps is where most physicists go awry. If a dust speck is in two locations at the same time, each one should create its own distortions in space-time, yielding two superposed gravitational fields. According to Penrose's theory, it takes energy to sustain these dual fields. The stability of a system depends on the amount of energy involved: the higher the energy required to sustain a system, the less stable it is. Over time, an unstable system tends to settle back to its simplest, lowest-energy state: in this case, one object in one location producing one gravitational field. If Penrose is right, gravity yanks objects back into a single location, without any need to invoke observers or parallel universes.

https://en.wikipedia.org/wiki/Penrose_interpretation
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#8
confused2 Offline
Back in the old days (1800ish) when Thomas Young was young they suspected light was waves but couldn't prove it and even if it was waves they had no way to find the wavelength.

Enter Thomas Young - discoverer of the Double Slit (also known as Young's Slits).

With his slits he could not only prove light was waves but also measure the wavelength of light.
Looking at
http://hyperphysics.phy-astr.gsu.edu/hba...slits.html
Where
d is the distance between slits
D is the distance to the screen
y is the distance between peaks
λ is the wavelength of the light
re-jigging their result we see (with some approximations)
λ=yd/D
The D,d and y were all easily measurable so he could measure the wavelength of light and become famous. Notice D,d and y are all lengths - it is pure geometry. If you try to introduce something that isn't pure geometry .. you'm likely making a mistake.

For a hundred years or so everyone was happy until Einstein came up with light being made out of photons (particles) that were indivisible at the point of birth and death. Just how a photon (a particle) could behave like a wave remains controversial to this day.

Here we see a physics 101 practical class two slit thingy:-
https://www.teachspin.com/two-slit

The result of counting photons:-


[Image: 3c5c71_2f00125584a24a30b1933ba0fa4c2736~mv2.gif]
[Image: 3c5c71_2f00125584a24a30b1933ba0fa4c2736~mv2.gif]


Calculated result here:-
http://hyperphysics.phy-astr.gsu.edu/hba...id.html#c2
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#9
Secular Sanity Offline
I still don’t understand what you’re getting at because like I said earlier, the individual photons still create an interference pattern until they’re detected, but even if the detector is absorbing photons like you said, the remaining ones that show up on the screen should still create a wave pattern but they don’t. Why is that? Like Jim Al-Khalili says in the video, if you can explain this using common sense and logic, there’s a noble prize waiting for you. Wink

Quote:Even though the individual scintillations (light pulse/flash) appear at random positions on the screen, their statistical behavior reproduces the original high-intensity diffraction pattern. Evidently the statistical behavior of the photons follows a predictable pattern, even though the behavior of individual photons is unpredictable. This implies that each individual photon, even though it behaves mostly like a particle, somehow carry with it a "knowledge" of the entire wavelike diffraction pattern. In some sense, a single photon must be able to go through both slits at the same time. This is what is known as the wave-particle duality for light: under appropriate circumstances light can behave as a wave or as a particle. source


https://www.youtube-nocookie.com/embed/A9tKncAdlHQ
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#10
confused2 Offline
SS Wrote:but even if the detector is absorbing photons like you said, the remaining ones that show up on the screen should still create a wave pattern but they don’t. Why is that?
I still don't understand the question. The 'wave pattern' that is seen in the Double Slit experiment when using single photons (or atoms) is inferred from the distribution of of the photons (or atoms) when they are detected. Most people seem to accept that the outcome is pure chance as though the particle is plucked out of the 'wave' most likely at the peaks and least likely at the troughs. This element of chance is what (I think) lead Einstein to say "God does not play dice."


There is a variation on Quantum Mechanics called Bohmian Mechanics. As I understand it Bohm proposed that there really is a wave as well as the particle - the idea being that the particle is guided by the wave - the particle chooses a path through the wave as a result of some 'property' which exists before the particle leaves the source. If you knew what the 'property' was you could predict the path exactly and all element of chance would be removed (no dice being rolled). The impossible things are 1/That the wave exists 2/That it vanishes without leaving a trace 3/That there is some 'property' (hidden variable) that changes the result from statistical to deterministic.

Clearly things (a lot of things) which are very strange (impossible?) are going on in quantum mechanics - which is what makes it fun (for me).

Feynman famously dealt with the problem of interpretation by saying "Shut up and calculate.". His path integral idea (see book QED) is the craziest of the lot and therefore (I think) most likely to be closest to the truth.
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